1. Field of the Invention
The present invention relates to organic electroluminescence device doping material (hereinafter, referred to as organic EL device doping material) suitable for doping a luminous layer of organic electroluminescence device (hereinafter referred to as organic EL device) and organic electroluminescence (EL) device having a luminous layer doped by the organic EL doping material.
2. Description of the Prior Art
An organic EL device has a thin film containing fluorescent organic compound sandwiched by a cathode and an anode. When electrons and electron holes are implanted for re-joining them, excitons are generated, and extinction of the excitons produces light emission (fluorescence, phosphorescence), which is utilized for display.
FIG. 6 shows an example of basic configuration of the organic EL device. This organic EL device is composed of a substrate 100, an anode 101, which is an indium tin oxide (ITO), a hole transporting layer 102 which is a derivative of triphenylamine, an organic luminous layer 103 which is tris (8-quinolinate) aluminum (III), and a cathode 104 which is an alloy of magnesium and silver. These components are stacked on one another in this order. Each of the organic layers has a thickness of about 50 nm. Each of the film-layers is formed by means of vacuum deposition. When voltage of 10 VDC is applied to this organic EL device, a green light emission of about 1000 cd/m2 can be obtained. This light emission is taken out from the ITO side. This organic EL device has a short service life and brightness is reduced to half after about 100 hours.
As for the organic EL devices which were developed prior to the organic EL device illustrated in FIG. 6, luminescence brightness obtained when it is driven by several tens of volts was only several cd/m2. The reason why the aforementioned EL device of FIG. 6 enables a high brightness is considered to be as follows.
1) The organic layer has a thickness as small as 100 nm for employing an organic material which is nearly an insulator in which the carrier movement is in the order of 10xe2x88x923 to 10xe2x88x925 cm/Vs.
2) A hole transporting layer is provided for isolating a function, thus enhancing rejoining in the luminous layer.
As for the reason why the organic EL device of FIG. 6 has a short service life, the following points are to be taken into consideration.
1) Physical Change of the Organic Layers
A crystalline grain boundary is generated in the organic films, especially in the hole transporting layer 102, which causes a short-circuiting.
2) Cathode 104 Oxidation/Peeling Out
As magnesium having a low work function is used, reaction is caused by humidity and oxygen in the device as well as humidity and oxygen in the air, thus generating oxide.
This significantly lowers electron implantation efficiency, and causes peeling out from the organic layer.
Afterwards, for obtaining multi-coloring the aforementioned organic EL device, a method was developed as follows. A coloring matter, or a pigment, such as coumarin and DCM was doped into the aforementioned organic luminous layer by several mol % so that these coloring matters generate electroluminescence. Because these coloring matters exhibit a high quantum yield of fluorescence, an external quantum yield was also improved. Such a doping for luminescence of a coloring matter is considered to be especially effective in the following cases.
1) In the band model, i.e., in the energy diagram, a HOMO level and a LUMO level of a dopant are found between the HOMO level and the LUMO level of the host material Alq,. This model is somehow applicable to organic cases.
2) The host material has a luminous spectrum which is mostly overlapped with the excitation spectrum of the dopant.
FIG. 7 is a schematic view of a structure of an organic EL device in which a pigment has been doped into an organic luminous layer 105 for multi-coloring. In this organic EL device, because Alq3 has a comparatively low fluorescence quantum yield, a fluorescent pigment having a high fluorescence quantum yield is doped into Alq3 by several percent mols., thus enhancing the device efficiency. Here, the dopant used may be an organic coloring matter or a pigment, for example, coumarin and DCM. Coumarin generates a blue-green light emission, whereas DCM generates an orange light emission. This EL device improves light emission efficiency as well as enables to realize multi-color emission. Even a material which causes concentration quenching can be used.
Recently, study is also made on an organic ED device using polyvinylcarbazole (PVK) as a host material. There is an example that a film was formed by way of dipping or a spin painting of PVK in which tetraphenylbutadiene (TPB), Nile red, and coumarin in solution are dispersed so as to form an electrode, and white luminescence was obtained. This case requires the same conditions as the organic EL device shown in FIG. 7, and should be soluble in a solvent.
A method has been suggested to obtain luminescence from a pigment by dispersing the pigment in polyvinylcarbazole (PVK). FIG. 8 shows a basic structure of the device in this case. The device is composed of a substrate 200, an anode 201 made of ITO, a luminous layer 202 made of PVK in which the pigment has been dispersed, and a cathode 203 made of Mg, Ag, and the like. These components are stacked on one another in this order. In this configuration, there is a single organic layer. It is also possible to provide an electron transporting layer between the luminous layer 202 and the cathode 203 As for the pigments for obtaining luminescence of colors. TPB, Coumarin 6, and Nile Red are used for obtaining blue color, green color, and red color, respectively. It is also possible to use these pigments simultaneously so as to obtain a white luminescence. The film of the organic layer is formed by the wet method such as dipping and spin coating. In the case of a single layer, the film thickness is 100 nm, whereas in the case of two layers, each of the layers is formed to have a thickness of about 50 nm.
The organic EL device has been studied in the direction of a multi-color type. The conventional dopant which has been doped in the organic luminous layer for the multi-color type of the organic EL device was a pigment. Pigments in general have a planar molecular structure and have a strong intermolecular force. Consequently, there is a problem that when a film is formed, a pigment easily agglutinates. For example, if a plenty of pigment is doped in Alq3 and a film is formed, the resultant luminous layer is turbid, lacks in stability, and has a low voltage resistance. That is, when it is used as a device, it is readily destroyed. Moreover, the conventional dopant is a pigment, which has a small molecular weight and a low melting point. Therefore, the resultant organic luminous layer of a formed film has insufficient heat resistance.
In view of the above-described problems, the present invention provides an organic EL device doping material having a high melting point and a thermal stability, improving stability of a corresponding organic luminous layer when doped; and an organic EL device containing such a doping material in the organic luminous layer.
An organic electroluminescence device doping material includes metal chelate complex composed of ligands having N Nxe2x80x2-bissalicylidene-2,3-diaminobenzofuran (SABF) skeleton.
An organic electroluminescence device doping material can be expressed by Chemical Formula 1, 
wherein X is a central metal ion, and R1 to R2, independently denote any one of hydrogen group, halogen group, alkyl group, cyano group, nitro group, ester group, amino group, mono- or disubstituted amino group, acylamino group, hydro group, alkoxy group, mercapto group, alkyloxy group, alkylthio group, aryloxy group, arylthio group, siloxy group, acyl group, cycloalkyl group, carbamoyl group, carboxylic group, sulfonate group, imide group, substituted or unsubstituted aliphatic group, substituted or unsubstituted aliphatic cyclic group, substituted or unsubstituted hydrocarbon aromatic group, substituted or unsubstituted heterocyclic aromatic cyclic group, and substituted or unsubstituted heterocyclic group.
An organic electroluminescence device doping material is characterized in that substituted or unsubstituted aliphatic cyclic ring, substituted or unsubstituted carbon cyclic aromatic ring, substituted or unsubstituted heterocyclic aromatic ring, and substituted or unsubstituted hetero cyclic ring are formed with the substituted groups in the neighborhood.
An organic electroluminescence device doping material is further characterized in that the central metal ion X is selected from a group consisting of Mg, Be, Ca, Zn, Al, Ga, In, Sr, Y, Sc, Ti, Zr, Cd, Ba, Sn, V, Co, Ag, Pb, Cu, and Au.
An organic electroluminescence device doping material can be expressed by Chemical Formula 2, 
wherein M1 is a central metal ion, and R1 to R14 independently denote any one of following groups independently but they are not restricted to only these substituted groups:
hydrogen group, halogen group, cyano group, nitro group, carboxyl group, sulfone group, acylamino group, ester group, mono- or disubstituted amino group, alkoxy group, mercapto group or methyl group, ethyl group, propyl group, butyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, octyl group, stearyl group, trichloromethyl group, aminomethyl group, acetoxymethyl group, acetoxyethyl group, acetoxypropyl group, acetoxybutyl group, hydroxymethyl group, hydroxyethyl group, hydroxypropyl group, hydroxybutyl group, vinyl group, styryl group, acetylene group, alkoxy group, mercapto group, alkyloxy group, alkylthio group, aryloxy group, arylthio group, siloxy group, acyl group, cycloalkyl group, substituted group such as carbamoyl group or substituted or unsubstituted acyclic hydrocarbon group, cyclopropyl group, cyclohexyl group, 1,3-cyclohexadienyl group, 2-cyclopentene-1-yl group, 2,4-cyclopentadiene-1-yl group, phenyl group, biphenylenyl group, triphenylenyl group, tetraphenylenyl group, 2-methylphenyl group, 3-nitro phenyl group, 4-methylthiophenyl group, 3,5-dicyanophenyl group, o-,m-, p-tolyl group, xylyl group, o-,m-,p-cumyl group, substituted or unsubstituted monocyclic hydrocarbon group such as mesityl group, pentalenyl group, indenyl group, napthyl group, azulenyl group, heptalenyl group, acenaphtylenyl group, phenalenyl group, fluorenyl group, anthryl group, anthraquinonyl group, 3-methylanthryl group, phenantolyl group, triphenylenyl group, pyrenyl group, crysenyl group, 2-ethyl-1-crysenyl, picenyl group, perilenyl group, 6-chloroperilenyl, pentaphenyl group, pentacenyl group, tetraphenylenyl group, hexaphenyl group, hexacenyl group, rubicenyl group, corronenyl group, trinaphthylenyl group, heptaphenyl group, heptasenyl, substituted or unsubstituted condensed polycyclic hydrocarbon group such as pentalenyl group and oparenyl group, thienyl group, furyl group, pyrrolyl group, imidazolyl group, pyrazolyl group, pyridyl group, pyrazinyl group, pyrimidinyl group, pyridazinyl group, indolyl group, quinolyl group, isoquinolyl group, phthalazinyl group, quinoxalynyl group, quinazolynyl group, carbazolyl group, acrydinyl group, phenadinyl group, furfuryl group, isothiazolyl group, isoquixazolyl group, furazanyl group, phenoquisadinyl group, benzthiazolyl group, benzoxazlyl group, benzoimidazolyl group, 2-methylpyridyl group, substituted or unsubstituted heterocyclic group such as 3-cyanopyridyl group or substituted or unsubstituted aromatic heterocyclic group, hydroxyl group, methoxy group, ethoxy group, propoxy group, butoxy group, sec-butoxy group, tert-butoxy group, pentyloxy group, hexyloxy group, stearyloxy group, phenoxy group, methylthio group, ethylthio group, propylthio group, butylthio group, sec-butylthio group, tert-butylthio group, pentylthio group, hexylthio group, heptylthio group, octylthio group, phenylthio group, amino group, methylamino group, dimethyl amino group, ethyl amino group, diethyl amino group, dipropyl amino group, dibutyl amino group, diphenyl amino group, bis(acetoxymethyl) amino group, bis(acetoxyethyl)amino group, bis(acetoxypropyl)amino group, bis(acetoxybutyl)amino group, dibenzyl amino group, methyl sulfamoyl group, dimethylsufamoyl group, ethyl sulfamoyl group, diethyl sulfamoyl group, propyl sulfamoyl group, butyl sulfamoyl group, pheny sulfamoyl group, diphenyl sulfamoyl group, ethyl carbamoyl group, diethyl carbamoyl group, propyl carbamoyl group, butyl carbamoyl group, phenyl carbamoyl group, methyl carbamoyl amino group, ethyl carbamoyl amino group, propyl carbamoyl amino group, butyl carbamoyl amino group, phenyl carbamnoyl amino group, methoxy carbamoyl amino group, ethoxy carbamoyl amino group, propyl carbamoyl amino group, butoxy carbamoyl amino group, phenoxy carbonyl group, 2-(2-ethoxyethoxy) ethoxy group, 2-(2-ethoxyethoxy) ethylthio group, 2-[2-methoxyethoxy)ethoxy]ethylthio group.
An organic electroluminescence device doping material can be expressed by Chemical Formula 3, 
wherein M2 is a center metal, and R1 to R14 are any one of following groups independently but they are not restricted to only these substituted groups:
hydrogen group, halogen group, cyano group, nitro group, carboxyl group, sulfone group, acylamino group, ester group, mono- or di-substituted amino group, alkoxy group, mercapto group or methyl group, ethyl group, propyl group, butyl group, secbutyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, octyl group, stearyl group, trichloromethyl group, aminomethyl group, acetoxymethyl group, acetoxyethyl group, acetoxypropyl group, acetoxybutyl group, hydroxymethyl group, hydroxyethyl group, hydroxypropyl group, hydroxybutyl group, stearyl group, vinyl group, styryl group, acetylene group, alkoxy group, mercapto group, alkyloxy group, alkylthio group, aryloxy group, arylthio group, siloxy group, acyl group, cycloalkyl group, substituted group such as carbamoyl group or substituted or unsubstituted acyclic hydrocarbon group, cyclopropyl group, cyclohexyl group, 1,3-cyclohexadienyl group, 2-cyclopentene-1-yl group, 2,4-cyclopentadiene-1-yl group, phenyl group, biphenylenyl group, triphenylenyl group, tetraphenylenyl group, 2-methylphenyl group, 3-nitrophenyl group, 4-methylthiophenyl group, 3,5-dicyanophenyl group, o-,m-,p-tolyl group, xylyl group, o-,m-,p-cumyl group, substituted or unsubstituted monocyclic hydrocarbon group such as mesityl group, pentalenyl group, indenyl group, naphthyl group, azulenyl group, heptylenyl group, acenaphthylenyl group, phenylenyl group, fluorenyl group, anthryl group, anthraquinonyl group, 3-methylanthryl group, phenantolyl group, triphenylenyl group, pyrenyl group, chrysenyl group, 2-ethyl-1-chrysenyl, picenyl group, perilenyl group, 6-chloroperilenyl, pentaphenyl group, pentacenyl group, tetraphenylenyl group, hexaphenyl group, hexacenyl group, rubicenyl group, corronenyl group, trinaphthylenyl group, heptaphenyl group, heptasenyl, substituted or unsubstituted condensed polycyclic hydrocarbon group such as pyranthrenyl group and oparenyl group, thienyl group, furyl group, pyrrolyl group, imidazolyl group, pyrazolyl group, pyridyl group, pyrazinyl group, pyrimidinyl group, pyridazinyl group, indolyl group, quinolyl group, isoquinolyl group, phthalazinyl group, quinoxalynyl group, quinazolynyl group, carbazolyl group, acrydinyl group, phenadinyl group, furfuryl group, isothiazolyl group, isoquinoxazolyl group, furazenyl group, phenoquinadinyl group, benzthiazolyl group, benzoxazolyl group, benzoimidazolyl group, 2-methylpyridyl group, substituted or unsubstituted heterocyclic group such as 3-cyanopyridyl group or substituted or unsubstituted aromatic heterocyclic group, hydroxyl group, methoxy group, ethoxy group, propoxy group, butoxy group, sec-butoxy group, tert-butoxy group, pentoxy group, hexyloxy group, stearyloxy group, phenoxy group, methylthio group, ethylthio group, propylthio group, butylthio group, sec-butylthio group, tert-butylthio group, pentylthio group, hexylthio group, heptylthio group, octylthio group, phenylthio group, amino group, methylamino group, dimethyl amino group, ethyl amino group, diethylamino group, dipropylamino group, dibutylamino group, diphenylamino group, bis(acetoxymethyl)amino group, bis(acetoxyethyl)amino group, bis(acetoxypropyl)amino group, bis(acetoxybutyl) amino group, dibenzylamino group, methylsulfamoyl group, ;dimethylsulfamoyl group, ethylsulfamoyl group, diethylsulfamoyl group, propylsulfamoyl group, butylsulfamoyl group, phenylsulfamoyl group, diphenylsulfamoyl group, ethyl carbamoyl group, diethylcarbamoyl group, propylcarbamoyl group, buty carbamoyl group, phenylcarbamoyl group, methylcarbamoyl amino group, ethylcarbamoyl amino group, propyl carbamoyl amino group, butylcarbamoyl amino group, phenylcarbamoyl amino group, methoxycarbamoyl amino group, ethoxycarbamoylamino group, propylcarbamoylamino group, butoxycarbamoylamino group, phenoxycarbonyl group, 2-(2-ethoxyethoxy)ethoxy group, 2-(2-ethoxyethoxy)ethylthio group, 2-[2-methoxyethoxy)ethoxy]ethylthio group.
An organic electroluminescence device doping material is characterized in that the central metal ion M2 is selected from a group consisting of Mg, Be, Ca, Zn, Al, Ga In, Sr, Y, Sc, Ti, Zr, Cd, Ba, Sn, V, Co, Ag, Pb, Cu, and Au.
An organic electroluminescence device doping material can be expressed by Chemical Formula 4, 
wherein M3 is a central metal ion, L is another ligand, and R1 to R14 are any one of following groups independently but they are not restricted to only these substituted groups:
hydrogen group, halogen group, cyano group, nitro group, carboxyl group, sulfone group, acylamino group, ester group, mono- or disubstituted amino group, alkoxy group, mercapto group or methyl group, ethyl group, propyl group, butyl group, secbutyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, octyl group, stearyl group, trichloromethyl group, aminomethyl group, acetoxymethyl group, acetoxyethyl group, acetoxypropyl group, acetoxybutyl group, hydroxymethyl group, hydroxyethyl, group, hydroxypropyl group, hydroxybutyl group, vinyl group, styryl group, acetylene group, alkoxy group, mercapto group, alkyloxy group, alkylthio group, aryloxy group, arylthio group, siloxy group, acyl group, cycloalkyl group, substituted group such as carbamoyl group or substituted or unsubstituted acyclic hydrocarbon group, cyclopropyl group, cyclohexyl group, 1,3-cyclohexadienyl group, 2-cyclopentene-1-yl group 2,4-cyclopentadiene-1-yl group, phenyl group, biphenylenyl group, triphenylenyl group, tetraphenylenyl group, 2-methyl phenyl group, 3-nitrophenyl group, 4-methylthiophenyl group, 3,5dicyanophenyl group, o-, m-, p-tolyl group, xylyl group, o-, m-, p-cumyl group, substituted or unsubstituted monocyclic hydrocarbon group such as mesityl group, pentalenyl group, indenyl group, naphthyl group, azulenyl group, heptalenyl group, acenaphthylenyl group, phenylenyl group, fluorenyl group, anthryl group, anthraquinonyl group, 3-methylanthryl group, phenantolyl group, triphenylenyl group, pyrenyl group, chrysenyl group, 2-ethyl-1-chrysenyl, picenyl group, perilenyl group, 6-chloroperilenyl, pentaphenyl group, pentacenyl group, tetraphenylenyl group, hexaphenyl group, hexacenyl group, rubicenyl group, corronenyl group, trinaphthylenyl group, heptaphenyl group, heptasenyl, substituted or unsubstituted condensed polycyclic hydrocarbon group such as pyranthrenyl group and oparenyl group, thienyl group, furyl group, Pyrrolyl group, imidazolyl group, pyrazolyl group, pyridyl group, pyrazinyl group, pyrimidinyl group, pyridazinyl group.
indolyl group, quinolyl group, isoquinolyl group, phthalazinyl group, quinoxalynyl group, quinazolynyl group, carbazolyl group, acrydinyl group, phenadinyl group, furfuryl group, isothiazolyl group, isoquinazolyl group, furazenyl group, phenoquinadinyl group, benzthiazolyl group, benzoxazlyl group, benzoimidazolyl group, 2-methylpyridyl group, substituted or unsubstituted heterocyclic group such as 3-cyanopyridyl group or substituted or unsubstituted aromatic heterocyclic group, hydroxyl group, methoxy group, ethoxy group, propoxy group, butoxy group, sec-butoxy group, tert-butoxy group, pentoxy group, hexyloxy group, stearyloxy group, phenoxy group, methylthio group, ethylthio group, propylthio group, butylthio group, sec, butylthio group, tert-butylthio group, pentylthio group, hexylthio group, heptylthio group, octylthio group, phenylthio group, amino group, methylamino group, dimethylamino group, ethylamino group, diethylamino group, dipropy amino group, dibutylamino group, diphenylamino group, bis(acetoxymethyl)amino group, bis(acetoxyethyl)amino group, bis(acetoxypropyl)amino group, bis(acetoxybutyl)amino group, dibenzylamino group, methyl sulfamoyl group, dimethylsufamoyl group, ethyl sulfamoyl group, diethylsulfamoyl group, propylsulfamoyl group, butylsulfamoyl group, phenylsulfamoyl group, diphenylsulfamoyl group, ethylcarbamoyl group, diethylcarbamoyl group, propylcarbamoyl group, butylcarbamoyl group, phenylcarbamoyl group, methyl carbamoyl amino group, ethylcarbamoyl amino group, propylcarbamoyl amino group, butyl carbamoyl amino group, phenylcarbamoyl amino group, methoxycarbamoyl amino group, ethoxycarbamoyl amino group, propylcarbamoyl amino group, butoxycarbamoyl amino group, phenoxycarbonyl group, 2-(2-ethoxyethoxy)ethoxy group, 2-(2-ethoxyethoxy)ethylthio group, 2-[2-methoxyethoxy)ethoxy]ethylthio group. An organic electroluminescence device doping material is characterized in that the central metal ion M3 is selected from the group consisting of Mg, Be, Ca, Zn, Al, Ga, In, Sr, Y, Sc, Ti, Zr, Cd, Ba, Sn, V, Co, Ag, Pb, Cu, and Au.
An organic electroluminescence divice doping material is characterizes in that the ligand L represents any one of a group consisting of phenol, derivative of phenol such as 4-phenylphenol, derivative of quinoline such as 2-methyl-8-quinolinol, 5-chloro 8-quinolinol, and 10-hydroxybenzene [h]quinoline, derivative of oxazole, derivative of oxadiazole, derivative of oxathiazole, derivative of triazole, derivative of coumarin, derivative of quinacridone, derivative of quinaldine, derivative of pyrene, derivative of stilylbenzene, aromatic amine, aliphatic amine, and aliphatic alcohol.
An organic electroluminescence device includes an organic luminous layer sandwiched between a pair of electrodes, at least one of which electrodes is translucent. Electrons and electron holes are implanted into the organic luminous layer so as to cause rejoining for generating excitons, extinction of which produces light emission which is utilized via the translucent electrode. The organic electroluminescence device is characterized in that the organic luminous layer contains the organic electroluminescence device doping material of the invention.
An organic electroluminescence device includes an electron implanted transporting layer, an organic luminous layer, and a hole transporting layer between a pair of electrodes, at least one of which electrodes is translucent. The organic luminous layer is made of a material selected from a group consisting of quinoline derivative, oxazole derivative, oxathiazole derivative, oxadiazole derivative, and triazole derivative; and contains the organic electroluminescence device doping material of the invention.
An organic electroluminescence device includes an electron implanted transporting layer and a hole implanted transporting layer which also functions as an organic luminous layer. These layers are sandwiched between a pair of electrodes, at least one of which is translucent. The hole implanted transporting layer is made of a material selected from a group consisting of triphenylamine derivative, phthalocyanine derivative, pyrazoline derivative, thiophenololigomer, polythiophene, polyparaphenylenevinylene, and polyvinylcarbazole. The organic luminous layer is prepared in such a way that a part of the hole implanted transporting layer which is in contact with the electron implanted transporting layer is doped with the organic electroluminescence device doping material of the invention.
An organic electroluminescence device is further characterized in that the organic electroluminescence device doping material of the invention is contained in the aforementioned organic luminous layer with a concentration of 0.01 to 10% by weight.